electric shower troubleshooting?

Triton t80xr shower has been working great, then out of the blue the pressure has dropped due to water coming out of the overflow hole on the bottom left hand corner of the shower unit, the shower is still flowing, although you cannot use it due to the overflow problem, the low pressure light is not on at all, have you encountered this problem before as i don't seem to be able to find any blogs for this fault, thanks